Manage your subscription

When the mind's eye processes language

The mind’s eye can develop a knack for language in people who have been blind since birth.

Functional magnetic resonance imaging (fMRI) measures blood flow in the brain to determine which neurons are most active. Since the 1990s the technology has shown, surprisingly, that the visual cortex flares up even in blind people. More puzzlingly, this activity occurs when they were carrying out language tasks.

Rebecca Saxe at the Massachusetts Institute of Technology says the result seemed implausible, because the visual cortex isn’t thought to be useful for language tasks. So to investigate, Saxe’s team invited both sighted adults and those who had been blind since birth to listen to speech while lying inside an fMRI scanner.

The team found that the language processing centres in the brains of all participants behaved almost identically, but the visual cortices of blind participants buzzed with far more activity than those of sighted people.

Advertisement

“This was kind of crazy,” says team member Evelina Fedorenko, also at MIT. “You have a portion of the brain which is there from birth to do something, but apparently it can acquire a new high-level function like language, which involves super complex cognitive processing.”

Linguistic boost

Fedorenko thinks that blind people who get a linguistic boost from their visual cortex might be better at language tasks than sighted people.

Amir Amedi of the Hebrew University of Jerusalem in Israel, who also studies how blind people use their visual cortices for other sensory functions, points out that this kind of brain flexibility is not unprecedented. Previous studies show that the brain can take a neural region devoted to one sense – sight, smell, hearing – and use it for another.

“Although that is amazing, the bottom line of this paper is that the brain can do something even more sensational than turning one sense into another,” he says. “A part of the brain spontaneously transforms just by the fact that one was born without vision. It’s very elegant.”